with my 2500 hd and 265/16 tires i can go to 20-25 and have no problem on soft sand at glamis or lake powell lone rock.Now if im towing a flatbed trailer with buggy at glamis i need to go to 15 all the way around.If at powell and need drag boat on soft stuff i go to 12psi and lower the boat trailer to about 20.
As for no camper and towing toyhualer (20ftr with 4 seat vw rail)3/4 mile across sand at glamis its 10-12 psi and trailer to 30 i have tried with 15 psi and couldnt make it got stuck had to go to 10psi.
Whoever mentioned pismo beach that sand feels softer i need to start at 10psi towing toyhauler(no camper)and 2 kid quads in bed of truck.